RCW 51.52.135

Worker or beneficiary entitled to interest on awardRate.

(1) When a worker or beneficiary prevails in an appeal by the employer to the board or in an appeal by the employer to the court from the decision and order of the board, the worker or beneficiary shall be entitled to interest at the rate of twelve percent per annum on the unpaid amount of the award after deducting the amount of attorney fees.
(2) When a worker or beneficiary prevails in an appeal by the worker or beneficiary to the board or the court regarding a claim for temporary total disability, the worker or beneficiary shall be entitled to interest at the rate of twelve percent per annum on the unpaid amount of the award after deducting the amount of attorney fees.
(3) The interest provided for in subsections (1) and (2) of this section shall accrue from the date of the department's order granting the award or denying payment of the award. The interest shall be paid by the party having the obligation to pay the award. The amount of interest to be paid shall be fixed by the board or court, as the case may be.
[ 1983 c 301 § 1.]